fix cartesian lookup

it seems that this was not working in 1.9 but we swallowed up the error
fixes #14437

lib/ansible/plugins/lookup/cartesian.py

@@ -50,5 +50,5 @@ class LookupModule(LookupBase):
         if len(my_list) == 0:
             raise AnsibleError("with_cartesian requires at least one element in each list")
 
-        return [self._flatten(x) for x in product(*my_list, fillvalue=None)]
+        return [self._flatten(x) for x in product(*my_list)]